BIOLOGY · Stage 7 · Chapter 2: Cells and Organisation
Biology 2.9 Tissues and organs in plants
5 min read 6 parts Lesson 9 of 10
Lesson summary
2.9 Tissues and organs in plants — Alhussan International Academy — Biology (Stages 7–9) notes: Describe how plant cells form tissues, organs and organ systems and name the main tissues in a leaf.Five levels — cells, tissues, organs, organ systems and the whole organism, from sma…
- Shoot system
- Root system
- Reproductive system
- Vascular bundles
- Order of layers
- Carbon dioxide
Section 1 of 6Levels of organisation in plants
- Five levels
- cells, tissues, organs, organ systems and the whole organism, from smallest to largest.
- Tissue
- a group of specialised plant cells of one type working together to carry out a function.
- Organ
- several tissues working together, such as a leaf.
- Organ system
- several organs working together, such as the shoot system.
Section 2 of 6Plant organ systems
- Shoot system
- the part above the ground, also called the photosynthetic system, which makes food.
- It includes the stems, leaves and flowers.
- Root system
- the part below the ground with two main functions.
- It anchors the plant in the soil so it does not fall over.
- It takes in the water and minerals the plant needs.
- Reproductive system
- plants also have this system, but in most plants it is present only for part of the year.
Section 3 of 6Plant organs
1Leaves4 points
- they make food by photosynthesis.
- They are usually green because their cells contain chloroplasts that trap light.
- They are often big and flat to trap as much light as possible.
- At night they take in oxygen and get rid of carbon dioxide from respiration.
2Stems3 points
- they support the plant.
- They hold the leaves up to catch sunlight and hold up flowers and fruit.
- They are sensitive to light and grow towards it.
3Roots2 points
- they absorb water and minerals and hold the plant in the ground.
- Some roots store food to help the plant survive hard conditions or reproduce.
4Flowers3 points
- they are the reproductive organs of a plant.
- They may be brightly coloured or strongly scented to make sure the plant reproduces.
- They count as organs because several tissues (petals, stamens, carpels) work together.
Section 4 of 6Plant tissues
| Tissue | Cells and function |
|---|---|
| Palisade (photosynthetic) tissue | Palisade cells with many chloroplasts, packed tightly near the top of the leaf, capture light for photosynthesis |
| Xylem | Dead cells forming hollow tubes that carry water and minerals up from the roots to the leaves and give support |
| Phloem | Living cells that carry sugars from the leaves, where they are made, to all the cells where they are needed |
- Location
- leaves, stems and roots all contain transport tissue.
- Vascular bundles
- xylem and phloem together form them.
- In a stem they are arranged in a ring.
- In roots they usually lie in the centre, which helps resist pulling forces.
Section 5 of 6The leaf as an organ
| Tissue | Role in the leaf |
|---|---|
| Waxy cuticle | Cuts down water loss |
| Upper epidermis | Thin, transparent protective layer that lets light through |
| Palisade mesophyll | Many chloroplasts, carries out most photosynthesis |
| Spongy mesophyll | Loosely packed cells with air spaces for gas diffusion |
| Xylem and phloem in veins | Bring water to the leaf and take sugars away |
| Lower epidermis with stomata and guard cells | Let gases in and out |
- Order of layers
- from the top, waxy cuticle, upper epidermis, palisade layer, spongy layer with veins, then lower epidermis with stomata.
Section 6 of 6How the tissues cooperate
- Water
- it travels from the roots up the xylem to the leaves.
- Carbon dioxide
- it diffuses in through open stomata and through the air spaces to the palisade cells.
- Sugars
- photosynthesis makes glucose, which is converted to sucrose and carried in the phloem to growing parts and to storage.
- Dependence
- roots cannot make sugar without the leaves, and leaves cannot work without water from the roots.
Last updated: